The copolymer composition comprising a long chain C6-C12 polyfluoroalkyl group (hereinafter called as “Rf group”) has been utilized previously as the water and oil resistant agent for paper.
On the other hand, US EPA (United State Environment Protection Agency) pointed out that the long chain Rf group produces perfluoro-octanoic acid (hereinafter called as “PFOA”) which might cause an influence on the environment.
Therefore, many efforts have been made to develop a water and oil resistant agent for paper by using a fluorine-containing copolymer having a short chain Rf group. The water resistance and the oil resistance, however, tend to decrease along with the decrease of the carbon number of the Rf group, and the water and oil resistance is not satisfactory. So, further improvements have to be made to provide a paper having an enough water and oil resistance.
Sugimoto et. al. (WO2009/057716), for example, proposed the water and oil resistant agent for paper comprising a fluorine-containing copolymer which contains, as essential polymer units, a fluorine-containing (meth)acrylate monomer having a C1-C6 Rf group, a polyalkylene glycol (meth)acrylate monomer and itaconic acid. The water and oil resistance of this agent has been improved fairy well. A further improvement, however, is still required to attain usual properties of the copolymer having a long chain Rf group.